Thin-strip casting device

ABSTRACT

A thin-strip casting device ( 1 ) assures across the entire selected range of the width an about constant production of thin-strip ( 12 ) without requiring artificially extended charging times of the steel plant installed upstream. A multitude of interchangeable pairs of casting rollers ( 2 ) having different casting roller diameters “D” depending on the strip width “B” to be cast, are associated with the thin-strip casting device ( 1 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of U.S. patent application Ser. No.10/010,528 filed on Dec. 7, 2001, hereby incorporated by reference, andwhich claims priority under 35 U.S.C. 119 of German No. 100 61 882.0filed on Dec. 12, 2000.

BACKGROUND

[0002] The invention relates to a thin-strip casting device comprised ofa pair of casting rollers that oppose each other and are approximatelyidentical. The casting rollers form a funnel by means of lateral sealsfor receiving the steel melt.

[0003] Thin-strip casting devices, in particular two-roller castingdevices for producing hot-rolled wide strip material in the usual widthrange of about 800 to 1400 mm and a thickness range of about 2 to 5 mmnormally found in such a production, are known in practical life.Casting rollers with a constant diameter and variable lengths of theirshells are normally employed because the width of the strip material issubstantially determined by the length of the shell of the castingrollers.

[0004] However, in the planning of a steel plant in the form of amini-foundry with an annual production capacity of about 400,000 to500,000 tons, which is installed upstream of the thin-strip castingplant and continuously supplies the latter with steel melt, theproduction of the steel foundry is practically constant. Therefore, thesteel plant is operating economically only if at least three to fivecharges are poured as “conti-conti” casts. This means that the steelfoundry has to be planned and designed in such a way that it is capableof supplying the thin-strip casting device with steel melt in acontinuous manner when the maximum strip width is desired. However, itmust also be accepted in the case where the steel foundry is operatedwith artificially prolonged charging times when small strip widths haveto be produced. This fact, however, impairs the economy of theproduction facility as a whole.

SUMMARY OF THE INVENTION

[0005] The object of the invention is to increase the capacity ofexisting thin-strip casting devices that are already operating withintheir limit, ranges, with low technical expenditure in terms ofmachinery and with justifiable investment expenditure. The objective isto avoid the drawbacks of the prior art described above to the extentthat a thin-strip casting device is provided that assures an aboutconstant production of thin-strip material over the entire selectedwidth range, without requiring artificially prolonged charging times ofthe steel foundry installed upstream.

[0006] The problem is solved by a multitude of pairs of interchangeablecasting rollers associated with the thin-strip casting device. Thesecasting rollers have different casting roll diameters depending on thestrip widths to be cast.

[0007] In an advantageous embodiment of the invention, each pair ofcasting rollers has a shell length defined by the strip width. A definedcasting roll diameter is chosen whereby the product of the shell lengthand the casting roller diameter “D” of the casting rollers of allinterchangeable pairs of casting rollers is approximately the same.

[0008] According to a useful further development of the invention, thepairs of casting rollers each are preinstalled in a changing frame.

[0009] Compared to known devices, the proposed thin-strip casting deviceoffers a substantial advantage in that it assures without much technicalexpenditure a constant production of thin-strip material in anycustomary width range and thus an economical operation of the steelfoundry operating upstream.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other objects and features of the present invention will becomeapparent from the following detailed description considered inconnection with.the accompanying drawings which disclose at least oneembodiment of the present invention. It should be understood, however,that the drawings are designed for the purpose of illustration only andnot as a definition of the limits of the invention.

[0011] In the drawings, wherein similar reference characters denotesimilar elements throughout the several views: FIG. 1a is a side view ofa thin-strip casting device in the form of a two-roller casting plant.

[0012]FIG. 1b is the view “A” according to FIG. 1a.

[0013]FIG. 2a shows the thin-strip casting device according to FIG. 1ain two schematically indicated variations, using differently designedcasting rollers.

[0014]FIG. 2b is the view “B” according to FIG. 2a.

[0015]FIG. 3 is the side view of a side seal for a pair of castingrollers; and

[0016]FIG. 4 shows the section C-C according to FIG. 3.

DESCRIPTION

[0017]FIGS. 1a and 1 b show a thin-strip casting device 1 in the form ofa two-roller casting device. Casting device 1 is comprised of a pair ofcasting rollers 2, which oppose each other and are approximatelyidentical. Casting rollers 2 are provided with a defined, predeterminedshell length, which approximately conforms to the strip width “B” andwith a defined, predetermined casting roller diameter “D”.

[0018] Casting rollers 2 form a funnel 5 by means of the associated sideseals 3, which each are arranged in mounting supports 4. Funnel 5 servesfor receiving steel melt 6, which is continuously supplied via anintermediate container 7 equipped with an immersion tube 8, by a steelfoundry that is located upstream and not shown in detail. Steel melt 6is filled into funnel 5, formed by casting rollers 2 and side seals 3 upto a defined bath level 9. The height of bath level 9 is also referredto as a solidification length “1” and defined by a bath level angle “a”.As casting rollers 2 are rotating, preferably in mutually oppositedirections, steel melt 6 solidifies on said rollers, forming two strandskins 10 or shells with a thickness “s”. Due to the rotation of castingrollers 2, two strand skins 10 are moved downwards and compressed at akiss point 11 or nip to form a thin-strip 12 with the strip thicknessd=2 * s. The casting rollers are preferably cooled. Thin-strip 12 exitsfrom thin-strip casting device 1 at the casting rate “v”, whichcorresponds to the peripheral speed of casting rollers 2. Furthermore,the following conditions have to be noted for thin-strip casting:Thickness “s” of two strand skins 10 approximately results from thefollowing known relation:

[0019] s =k *tn whereby “k” is a constant depending on the coolingconditions, and “t” is the solidification time.

[0020] A value of from 0.5 to 1.0 can be assumed for “n”, whereby n 0.5applies to a constant surface temperature (conventional continuouscasting), and n =1.0 applies to a constant temperature gradient instrand skin 10, thus to a highly decreasing surface temperature of saidskin.

[0021] A highly decreasing surface temperature of strand skin 10 isexpected in thin-strip casting, and it has been found that in thethickness range of up to about 5 mm, n =1 applies at least byapproximation, and-thus s =k * t applies accordingly. Furthermore, afterevaluating extensive tests and the trade literature it was found thatfor thin-strip casting in the thickness range of up to 5 mm, with “t” inseconds and “5” in mm, the constant for the very rapid initialsolidification of strand skins 10 comes to “k”=2.5. Accordingly, thefollowing conditions now apply:

s=2.5 * t

d=2 * s, and accordingly

d=5 * t, or t=d/5.

[0022] It is known that the following applies to the casting rate “v”:v=l/t, whereby solidification length l results in the following at abath level angle “α” of 45°: l=(Π* D * 45)/360=0.39 * D. With t=d/5, thefollowing is obtained for “v” in m/s (“D” in m and “d” in mm):

v=(0.39 * D * 5)/d=(1.95 * D)/d,

[0023] and accordingly the following is obtained for “v” in dm/s as wellas “D” and “d” in dm: v=(1.95 * D)/(d * 100).

[0024] As demonstrated above, casting rate “v” of thin-strip castingdevice 1 is proportional to diameter “D” of casting rollers 2 andinversely proportional to strip thickness “d”.

[0025] The production “P” of thin-strip casting device 1, measured inkg/s, is obtained in dependence of strip width “B” and strip thickness“d” (each in dm), casting rate “v” (in dm/s) and the density for steelof 7.8 kg/dm³ from the following relation:

P=B * d * v * 7.8.

[0026] Furthermore, taking into account the above conditions withrespect to “v”, the following is obtained for production “P”:

P=B * 1.95 * D * 0.078.

[0027] Furthermore, it was found that the production of thin-stripcasting device 1 is proportional to strip width “B” and diameter “D” ofcasting rollers 2.

[0028] Now, based on the evaluation of the conditions specified above,an approximately constant production “P” that is coordinated with asteel foundry located upstream, can be achieved according to theinvention by associating with thin-strip casting device 1 a multitude ofinterchangeable pairs of casting rollers 2, whereby pairs of castingrollers 2 each have a different casting roller diameter “D” depending onband widths “B” to be cast.

[0029]FIGS. 2a and 2 b show a comparison of a side view and a top viewon the left side casting roller 2 of a pair of casting rollers 2 forproducing a wide thin-strip 12, and on the right side casting roller 2of a pair of casting rollers 2 for producing a narrow thin-strip 12,because the length of the shell of casting rollers 2 is known to bedefined or determined by selected strip width “B”. Furthermore, castingroller 2 drawn on the left side for the wide thin-strip 12 has a smallercasting roller diameter “D” than casting roller 2 drawn on the rightside.

[0030] The invention assures an approximately constant production ofthin-strip 12 over the entire range selected for the width withoutrequiring any artificially extended charging times of the steel foundrylocated upstream. Strip width “B” or jacket length, and casting rollerdiameter “D” of each pair of casting rollers 2 are selected in such amanner that the product of the jacket length and casting roller diameter“D”,of all interchangeable pairs of casting rollers 2 is approximatelythe same.

[0031] The invention is explained by way of example in even greaterdetail in the following. For a mini-foundry comprising an electric steelplant and thin-strip casting device 1 for producing hot-rolled stripmaterial with an annual production capacity of about 500,000 tons in thewidth range from 800 to 1400 mm strip width “B”, provision has to bemade in the prior art for a steel foundry with an hourly productioncapacity of about 90 tons, and thin-strip casting device 1 with acasting roller diameter “D” of about 1.2 m. Based on a selected stripwidth “B” of 1,400 mm and the casting roller diameter “D” of 1.2 mspecified above, the thin-strip casting device has an hourly productionoutput of 90 tons as well. However, for strip widths of less than 1,400mm, the hourly production output of thin-strip casting device 1 islower, so that the steel foundry, as explained above, has to be operatedfor the required continued continual supply of thin-strip casting device1 with artificial pauses between the charges. With such a plant design,the annual production capacity then ensuing from the mean hourlycapacity of thinstrip casting device 1 comes to between about 52 tons at800 mm strip width, and, as specified above, to about 90 tons at 1,400mm strip width “B”.

[0032] With the measures as defined by the invention, which is tosubstantially employ different casting roller diameters “D” fordifferent strip widths “B”, a mini-foundry can be planned, for examplefor about 500,000 tons annual production capacity and strip widths “B”to be produced in the range of from 800 to 1,400 m. The electric steelplant outputs about 70 tons hourly and thin-strip casting device 1 hascasting roller diameters “D” selected, for example with 1.4 m for stripwidths “B” of 800 to 1,000 mm; 1.2 m for strip widths “B” of from 1,000to 1,200 mm; and 1.0 m for strip width “B” of from 1,200 to 1,400 mm.With such a design, the hourly production capacity of thin-strip castingdevice 1 is adapted over the entire width range to the hourly-productionoutput of the steel plant.

[0033] Artificial pause times of the steel plant between the individualcharges are now no longer required in order to assure a continuousproduction “p”.

[0034]FIGS. 2a and 2 b furthermore show that for the purpose of a morepractical handling of the pairs of casting rollers 2, i.e. for theirinterchange depending on the selected strip width “B” to be cast, pairsof casting rollers 2 each may be pre-installed in a change frame 13 thatis mounted in a fixed, but detachable manner on a base frame-not shownin greater detail-of thin-strip casting device 1. Change frame 13,furthermore, may have the same outside dimensions for all dimensionsused for casting rollers 2 employed (FIG. 2b).

[0035] Furthermore, change frame 13 supports setting frames 14-which areknown per se-for bearings 15 of the casting rollers 2. Setting frames 14can be set to desired strip thickness “d”, for example by means of thehydraulically or pneumatically actuated setting cylinders 16.

[0036] Holding elements 4 for the side seals 3-which are known per seand not shown in greater detail in FIGS. 2a and 2 b -of pairs of castingrollers 2 are mounted on support surfaces 17 of change frame 13. Lateralseals 3 are known to be substantially formed by outer frame 18 that islined with a cast refractory compound 19 (FIGS. 3 and 4). On both sidesof casting rollers 2, insert 20 consisting of a special ceramicmaterial, for example boron nitride, is embedded on each side inrefractory compound 19. Inserts 20 envelop the peripheral tracks ofcasting rollers 2 disposed below bath level 9.

[0037] Suitably adapted lateral seals 3 may be associated with thedifferent diameters “D” of the casting rollers. Furthermore, it ispossible also to design lateral seals 3 in such a manner that the samelateral seals 3 may be associated with pairs of casting rollers 2 havingthe different casting roller diameters “D”, by designing, for exampleinserts 20 in a variable manner in the zone of the peripheral surfacesof casting rollers 2, such inserts enveloping the latter.

[0038] The same may apply to holding elements 4 of lateral seals 3,which may be adaptable to changed casting roller diameters “D” and, ifneed be, to variably designed lateral seals 3, as well as to changedshell lengths of casting rollers 2, by adjustably and lockably guidingsaid holding elements vertically and/(or horizontally and/or radially inguide elements such as, for example rails, which are not shown indetail, but known per se.

[0039] As far as change frame 13 is concerned, it is recommended toprovide two change frames 13, of which the one frame is in use with acorresponding pair of casting rollers 2, and the other is being preparedwith a corresponding pair of casting rollers 2 and new lateral seals 3for the next change.

[0040] Accordingly, while at least one embodiment of the presentinvention has been shown and described, it is to be understood that manychanges and modifications may be made thereunto without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A thin-strip casting device that is supplied withsteel melt from a steel foundry, the thin-strip casting devicecomprising: a. at least one pair of pivotably supported parallel castingrollers axially spaced adjacent to each other so as to define a kisspoint for receiving steel melt, wherein said casting rollers haveapproximately the same design, rotate in mutually opposite directions,and have a predetermined length which relates to a resulting stripwidth; and b. lateral seals disposed at each lateral end of said atleast one pair of casting rollers so as to form a funnel area betweensaid pair of casting rollers and said lateral seals; wherein a multitudeof interchangeable pairs of casting rollers are associated with thethin-strip casting device and said pairs of casting rollers havedifferent diameters based on their widths.
 2. The thin-strip castingdevice according to claim 1, wherein each of said pair of castingrollers has a shell length defined by the strip width and a diameterdefined so that the product of said shell length and said diameter ofevery pair of casting rollers in the thin-strip casting device isapproximately the same.
 3. The thin-strip casting device according toclaim 1 further comprising: a. a holding element disposed on the outerend of each lateral seal, wherein said holding element holds the lateralseal in the thin-strip casting device; b. at least one bearing elementthat runs through each casting roller, wherein said at least one bearingelement allows said casting roller to rotate around it; c. settingframes in which the ends of said at least one bearing element areinstalled; and d. a change frame in which said pair of casting rollersare situated and upon which said holding element and said setting framesare installed.
 4. The thin-strip casting device according to claim 3wherein said setting frames are set to create a desired strip thicknessby means of a hydraulically activated setting cylinder, wherein saidcylinder is disposed in said setting frame and said cylinder moves saidat least one pair of casting rollers closer together or further apart.5. The thin-strip casting device according to claim 3, wherein saidsetting frames are set to create a desired strip thickness by means of apneumatically activated setting cylinder, wherein said cylinder isdisposed in said setting frame and said cylinder moves said at least onepair of casting rollers closer together or further apart.
 6. Thethin-strip casting device according to claim 3, wherein said holdingelements are mounted on support surfaces of said change frame.
 7. Thethin-strip casting device according to claim 1, wherein said lateralseals comprise: a. an outer frame that surrounds said lateral seal thatis lined with a cast refractor compound; and b. an insert disposed onthe inside of said lateral seal made of a ceramic material thatenvelopes the track of said casting roller below said bath height. 8.The thin-strip casting device according to claim 3, wherein said lateralseals are adaptable to casting rollers with different diameters byhaving a wider space in said inserts at the peripheral surface of saidcasting rollers to envelope said casting rollers.
 9. The thin-stripcasting device according to claim 8, wherein said lateral seals areadaptable to casting rollers of different diameters by adjustablyguiding said holding elements on guide elements to meet different shelllengths.
 10. The thin-strip casting device according to claim 3, whereintwo change frames are used so that while one change frame is in use theother is prepared with a pair of casting rollers and lateral seals forthe production of the next thin-strip.
 11. The thin-strip casting deviceaccording to claim 1, wherein said at least one pair of casting rollersare cooled.